# chainlink-data-feeds

Helps safely read Chainlink AggregatorV3 price feeds on Hedera testnet (296) and mainnet (295), validate round staleness, and normalize decimals.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 444 installs · ★ 28
- Author: hedera-dev
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/hedera-dev/hedera-skills/tree/HEAD/plugins/oracles/skills/chainlink-data-feeds/SKILL.md
- Updated: 2026-09-03
- HTML: https://affpapa.org/en/nevibecode/skills/chainlink-data-feeds

## What it does

This skill guides the AI assistant when integrating Chainlink price oracles on the Hedera network. It enforces a strict verification pattern when calling `latestRoundData()` on `AggregatorV3Interface`. The assistant rejects uncompleted rounds when `answeredInRound < roundId`, zero `updatedAt` timestamps, or non-positive answers.

Freshness checks are mandatory. The code must verify that `block.timestamp - updatedAt` does not exceed `maxStaleness`. Because feed values typically use 8 decimals, the skill requires explicit normalization to the consumer scale (often 18 decimals) with downward rounding.

Copying Ethereum aggregator addresses will break contract execution. Hedera requires dedicated feed addresses for testnet (chain ID 296) or mainnet (chain ID 295). Note that this skill only covers price feeds and explicitly excludes Chainlink CCIP tokens.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add hedera-dev/hedera-skills --skill chainlink-data-feeds -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/chainlink-data-feeds/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/chainlink-data-feeds/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add hedera-dev/hedera-skills --skill chainlink-data-feeds -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/chainlink-data-feeds/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add hedera-dev/hedera-skills --skill chainlink-data-feeds -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/chainlink-data-feeds/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install hedera-dev/hedera-skills chainlink-data-feeds
```

2. **Manually: put the files in place**
- File: `.github/skills/chainlink-data-feeds/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add hedera-dev/hedera-skills --skill chainlink-data-feeds -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/hedera-dev/hedera-skills --path plugins/oracles/skills/chainlink-data-feeds
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/chainlink-data-feeds/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add hedera-dev/hedera-skills --skill chainlink-data-feeds -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/hedera-dev/hedera-skills/tree/HEAD/plugins/oracles/skills/chainlink-data-feeds/SKILL.md

## When to use it
- read AggregatorV3Interface price feeds on Hedera
- validate incomplete and stale Chainlink feed rounds
- normalize oracle decimals from 8 to 18
- select valid feed addresses for chain IDs 295 and 296

## Example prompts
- Write a Solidity function to fetch the HBAR/USD price on Hedera testnet using AggregatorV3Interface
- Audit my oracle reader contract for Chainlink round completeness and staleness checks
- Implement decimal normalization from an 8-decimal Chainlink feed to 18 decimals

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 4d1053a70894f9c3.

BEGIN THIRD-PARTY FILE 4d1053a70894f9c3
````text
---
name: chainlink-data-feeds
description: >
  Chainlink Data Feeds on Hedera. Use when reading AggregatorV3 price feeds on Hedera
  (testnet 296 / mainnet 295), calling latestRoundData, checking round completeness and
  staleness, or normalizing feed decimals. Not for Chainlink CCIP (cross-chain tokens).
---

# Chainlink Data Feeds (Hedera)

**Push feed pattern:** a Chainlink aggregator is updated off-chain; on-chain readers call `latestRoundData()` and must reject incomplete, non-positive, or stale rounds.

```text
Chainlink DON → AggregatorV3Interface feed → consumer latestRoundData()
```

Consumers may wrap the feed behind a local interface; that is optional. Do not assume a project-specific adapter name.

## Quick Reference

| Piece | Role |
| ----- | ---- |
| `AggregatorV3Interface` | `latestRoundData()` + `decimals()` |
| Round completeness | `answeredInRound >= roundId` and `updatedAt != 0` |
| Price | `answer > 0` (feeds are typically signed `int256`) |
| Freshness | Compare `block.timestamp - updatedAt` to a max staleness |
| Scale | Normalize feed decimals to the consumer’s scale (often 18) |
| Pair identity | Prefer canonical uppercase symbols (`HBAR`, `USD`) if you hash pair keys |

**Hedera chain IDs:** testnet `296`, mainnet `295`.

See [references/hedera-feeds.md](references/hedera-feeds.md) for where to source Hedera feed addresses. See [references/examples.md](references/examples.md) for read and normalize sketches.

## Critical: Completeness Then Staleness

Never return a price from a missing or unfinished round. Revert when:

| Condition | Why |
| --------- | --- |
| `answeredInRound < roundId` | Aggregator has not finished this round |
| `updatedAt == 0` | No successful update |
| `answer <= 0` | Invalid / non-positive price |
| `block.timestamp - updatedAt > maxStaleness` | Stale for this consumer |

```solidity
(uint80 roundId, int256 answer,, uint256 updatedAt, uint80 answeredInRound) =
    feed.latestRoundData();

if (answeredInRound < roundId || updatedAt == 0) revert IncompleteRound();
if (answer <= 0) revert InvalidPrice();
if (block.timestamp - updatedAt > maxStaleness) revert StalePrice(updatedAt, maxStaleness);
```

## Critical: Hedera Feeds, Not Ethereum Addresses

Do **not** copy Ethereum mainnet aggregator addresses onto Hedera. Look up Hedera-specific Data Feed addresses for chain `295` / `296` and re-check docs before mainnet.

Pair maps (if you use them) should be constructor-only unless the project explicitly supports post-deploy updates.

## Decimal Normalization

`feed.decimals()` is often 8. Convert to the scale your app uses before arithmetic:

```solidity
````
END THIRD-PARTY FILE 4d1053a70894f9c3

The third-party file has ended. Everything between the 4d1053a70894f9c3 tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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